Many lateral flow assay devices and methods are known in the art. Typically, the devices and methods allow for application of a sample to a lateral flow matrix. The sample flows along the lateral flow matrix, and one or more analyte components to be detected in the sample react with at least one reagent which is provided in or added to the lateral flow matrix. At least one reagent is typically immobilized in the device for reaction with the analyte component to be detected or a reagent thereof, and labels are typically employed to measure the extent of reaction with an immobilized reagent.
For example, the Dafforn et al U.S. Pat. No. 4,981,786 discloses an assay device for capturing a first member of a specific binding pair in a zone and for allowing liquid to be carried by capillary action away from the zone. A liquid reagent for conducting the assay, for example comprising a specific binding pair member, members of a signal producing system, ancillary reagents, or the like, is added. Dafforn et al disclose the specific use of their assay device and method for detecting the presence of human chorionic gonadotrophin (HCG).
To facilitate use of lateral flow assay devices by laboratory personnel and by non-laboratory medical personnel and consumers, for example in “point of care” applications, and to obtain quicker detection techniques, much attention has been directed to improving one-step assay devices and methods. For example, the May et al U.S. Pat. Nos. 5,602,040, 5,622,871, 5,656,503, 6,187,598 and 6,228,660 disclose devices, kits and methods which facilitate one-step lateral flow assay methods. A test strip is provided with a dried labeled reagent which is released into a mobile form by a liquid biological sample. The labeled reagent specifically binds with the analyte to be detected to form a complex, and the migration of the liquid sample along the lateral flow matrix conveys the complex by capillary action to a detection zone.
The Hubscher et al U.S. Pat. No. 6,528,325 discloses a more specific device and method for detection of antibodies in human serum by use of a lateral flow assay which facilitates one step techniques. A test sample obtained from bodily fluids reacts with a gold labeled antigen and the resulting complex travels across a membrane and along a lateral flow strip. Red colored lines formed in specific locations along the test strip indicate the presence of class specific antibodies in the test specimen. In a more specific embodiment disclosed by Hubscher et al, the lateral flow assay serves as an immunochromatographic screening test for the detection of allergen-specific IgE antibodies in human serum. Test sample reacts with gold labeled anti-IgE antibody and the resulting complex travels across the membrane where immobilized allergens capture the allergen specific IgE complex. Colored lines are formed in the test areas to indicate the presence of allergen-specific IgE antibodies.
Detection of specific allergies in an individual is important in allowing medical personnel to prescribe safe and effective allergy treatment. Common techniques for allergy detection typically involve skin prick testing to expose an individual to various allergens and/or complex and expensive laboratory testing. Because of the trauma, cost and/or inconvenience of commonly employed techniques, many medical personnel prescribe allergy treatments based only on an individual's symptoms, without testing to determine what specific allergies the individual may have. Such prescriptions obviously can be dangerous, wasteful and/or ineffective as individuals can be prescribed treatment medicines which are not proper for their allergy conditions. Accordingly, it would be advantageous to use lateral flow assay techniques for detection of IgE antibodies of an individual for accurate diagnosis of allergy in an individual. However, detection of specific IgE antibodies is often difficult. That is, biological samples such as blood contain a plurality of nonspecific binding members which interfere with reactions necessary for accurate labeling and detection of specific IgE antibodies.
More particularly, determination of a specific allergy requires identification of an IgE antibody having a variable region which binds to a specific allergen epitope. Bodily fluids typically contain thousands of antibodies of different IgE variable region specificities, and therefore, determination of a specific allergy by assay requires selective reaction of a single antibody type from the thousands of IgE antibody specificities. Detection conjugates readily bind to the constant regions of such IgE antibodies, i.e., the detection conjugates typically do not differentiate between different IgE specificities, and identification of a particular IgE antibody is difficult using conventional assay and label techniques. In practice, it has been difficult to conduct lateral assays using techniques as disclosed in the prior art to reliably identify IgE of an individual for diagnosing allergy. Typically, an immunoassay based on allergens bound on a solid phase, employing a detection conjugate binding to the non-variable region of IgE antibodies in the assay, will be sensitive to non-specific binding of IgE in the assay. Accordingly, a need exists for improved assay devices and methods, particularly for facilitating detection of specific IgE antibodies.